Is there an order summoning of the adds in this fight? I know Icy Veins says that it's random, but from a cursory examination of the log from our first 6 attempts last night, it looks like he was always starting with Arcweaver / Ironblade combo and then following up with Assassin / Warshaman. But it's a bit tricky to be sure as there isn't a summon log event so I'm searching for deaths of the adds

As for the answer, I can't check myself, since I'm at work, but I'd imagine that watching a few youtube videos of the fight should confirm whether or not the spawns are random -- no need to look at logs.

Edit: After checking logs, it appears that the first two waves were always the ones you listed, so I'm guessing it might not actually be random. Here's the order from our 25m kill last Tuesday:Arcweaver/IronbladeAssassin/WarshamanAssassin/IronbladeArcweaver/WarshamanIronbalde/WarshamanArcweaver/Assassin

At that point, we had the boss around 10%, or whatever the trigger is for adds to start spawning in 3s, so I won't list anything further.

Now this might change week on week, but for that week at least it was consistent. We killed it last night but I didn't have a personal log running and I can't do my manipulation on WoL logs so I can't confirm anything more. From memory it did seem to always start Arcweaver Ironblade, but we two shot it so not a massive sample size.